An image obtainer, a distance detector, a computer, and an information provider are provided to a vehicle. The computer has a caution-determination function to determine whether caution is required with respect to objects existing around the vehicle by arithmetically processing image data and distance data, and an information providing function to output an instruction to provide information to the occupants of the vehicle by the information provider when it is determined that caution is required. A reference axis for obtaining image is positioned at the center of a range of obtaining the image data by the image obtainer, and a reference axis for detecting distance is positioned at the center of a range of detecting the distance data by the distance detector. The image obtainer and the distance detector are arranged such that the reference axes are coaxially aligned.